The demand and value of 1,3-butadiene, which is used as an intermediate of petrochemical products in the petrochemical market, has been gradually increasing worldwide. Methods of producing 1,3-butadiene may largely include naphtha cracking, direct dehydrogenation of n-butene, and oxidative dehydrogenation of n-butene. Among them, a naphtha cracking process is problematic in that a large amount of energy is consumed due to high reaction temperature and in that a new naphtha cracker must be installed to meet the increased demand for 1,3-butadiene. Further, a naphtha cracking process is problematic in that the naphtha cracking process is not an independent process for producing only 1,3-butadiene, so that the investment and operation for a naphtha cracker cannot be optimally matched with the production and demand of 1,3-butadiene, and other basic fractions besides 1,3-butadiene are excessively produced. Therefore, an independent process for producing only 1,3-butadiene is required. As an alternative of the independent process, there is a method of producing 1,3-butadiene by a hydrogenation reaction of n-butene. The dehydrogenation reaction of n-butene includes a direct dehydrogenation reaction and an oxidative dehydrogenation reaction. Since the direct dehydrogenation reaction of n-butene is an endothermic reaction, it requires high-temperature reaction conditions and thermodynamic low-pressure reaction conditions, and thus the yield of 1,3-butadiene is very low, so that it is not suitable as a commercial process [M. A. Chaar, D. Patel, H. H. Kung, J. Catal., volume 109, page 463 (1988)/E. A. Mamedov, V. C. Corberan, Appl. Catal. A, volume 127, page 1 (1995)/L. M. Madeira, M. F. Portela, Catal. Rev., volume 44, page 247 (2002)].
Therefore, an oxidative dehydrogenation reaction of n-butene is gradually considered as an effective alternative which is an independent process and can flexibly cope with the change in a situation of the market of 1,3-butadiene. The oxidative dehydrogenation reaction of n-butene, which is a reaction obtaining 1,3-butadiene and water by reacting n-butene with oxygen, is thermodynamically advantageous because stable water is formed as a reaction product. Further, the oxidative dehydration of n-butene is advantageous compared to the direct dehydration of n-butene in that a high yield of 1,3-butadiene can be obtained even at low reaction temperature because the oxidative dehydration of n-butene is an exothermic reaction, whereas the direct dehydration of n-butene is an endothermic reaction, and in that it can be commercially used because it does not need an additional heat supply. Therefore, a process of producing 1,3-butadiene using the oxidative dehydrogenation reaction of n-butene can become an effective independent process capable of satisfying the increasing demand for 1,3-butadiene. In particular, the process of producing 1,3-butadiene using the oxidative dehydrogenation reaction of n-butene is advantageous in that, in the case where a catalyst which can obtain a high yield of 1,3-butadiene even when a C4 mixture including impurities, such as n-butane and the like, is used as a reactant, a C4 raffinate-3 mixture or a C4 mixture can be practically used as a supply source of n-butene, and thus a cheap surplus C4 fraction can be made into high value-added products.
As described above, since the oxidative dehydrogenation reaction of n-butene is a reaction obtaining 1,3-butadiene and water by reacting n-butene with oxygen and has many advantages compared to other processes for producing 1,3-butadiene, it can become an alternative for producing only 1,3-butadiene. Nevertheless, many side reactions, such as complete oxidation and the like, are expected to occur because oxygen is used as a reactant in the oxidative dehydrogenation reaction of n-butene, so that it is most important to develop a catalyst which can maintain high activity by controlling oxidation capacity, suppress side reactions to the highest degree and increase the selectivity of 1,3-butadiene.
Up to date, examples of catalysts used the oxidative dehydrogenation of n-butane include bismuth molybdate-based catalysts [A. C. A. M. Bleijenberg, B. C. Lippens, G. C. A. Schuit, J. Catal., volume 4, page 581 (1965)/Ph. A. Batist, B. C. Lippens, G. C. A. Schuit, J. Catal., volume 5, page 55 (1966)/M. W. J. Wolfs, Ph. A. Batist, J. Catal., volume 32, page 25 (1974)/W. J. Linn, A. W. Sleight, J. Catal., volume 41, page 134 (1976)/W. Ueda, K. Asakawa, C.-L. Chen, Y. Moro-oka, T. Ikawa, J. Catal., volume 101, page 360 (1986)/J. C. Jung, H. Kim, A. S. Choi, Y.-M. Chung, T. J. Kim, S. J. Lee, S.-H. Oh, I. K. Song, J. Mol. Catal. A, volume 259, page 166 (2006) Y. Moro-oka, W. Ueda, Adv. Catal., volume 40, page 233 (1994)/R. K. Grasselli, Handbook of Heterogeneous Catalysis, volume 5, page 2302 (1997)]; ferrite-based catalysts [R. J. Rennard, W. L. Kehl, J. Catal., volume 21, page 282 (1971)/W. R. Cares, J. W. Hightower, J. Catal., volume 23, page 193 (1971)/M. A. Gibson, J. W. Hightower, J. Catal., volume 41, page 420 (1976)/H. H. Kung, M. C. Kung, Adv. Catal., volume 33, page 159 (1985)/J. A. Toledo, M. A. Valenzuela, H. Armendariz, G. Aguilar-Rios, B. Zapzta, A. Montoya, N. Nava, P. Salas, I. Schifter, Catal. Lett., volume 30, page 279 (1995)]; tin-based catalysts [Y. M. Bakshi, R. N. Gur'yanova, A. N. Mal'yan, A. I. Gel'bshteirt, Petroleum Chemistry U.S.S.R., volume 7, page 177 (1967)]; and the like.
The reaction mechanism of the oxidative dehydrogenation reaction of n-butene has been never accurately known, but it is known that C—H bonds are cut from n-butene and simultaneously the oxidation-reduction reaction of the catalyst itself occurs. Therefore, composite oxide catalysts having a specific crystal structure including metal ions having various oxidation states have been used in the oxidative hydrogenation reaction [W. R. Cares, J. W. Hightower, J. Catal., volume 23, page 193 (1971)]. Therefore, all of the above catalysts are composite oxide catalysts having a specific crystal structure. Among the above catalysts, bismuth molybdate-based catalysts and ferrite-based catalysts were reported to exhibit high activity in the oxidative dehydrogenation reaction of n-butene [F.-Y. Qiu, L.-T. Wong, E. Sham, P. Ruiz, B. Delmon, Appl. Catal, volume 51, page 235 (1989)/B. Grzybowska, J. Haber, J. Komorek, J. Catal., volume 25, page 25 (1972)/J. C. Jung, H. Kim, Y. S. Kim, Y.-M. Chung, T. J. Kim, S. J. Lee, S.-H. Oh, I. K. Song, Appl. Catal. A, volume 317, page 244 (2007)].
Among the composite oxide catalysts used in the oxidative dehydrogenation of n-butene, bismuth molybdate-based catalysts include pure bismuth molybdate catalysts made of only bismuth and molybdenum oxide and multi-component bismuth molybdate catalysts made by adding various metal components to the pure bismuth molybdate catalysts. The pure bismuth molybdate catalysts exist in several phases. It is known that the pure bismuth molybdate catalysts existing in three phases, such as α-bismuth molybdate (Bi2Mo3O12), β-bismuth molybdate (Bi2Mo2O9) and γ-bismuth molybdate (Bi2MoO6), can be practically used [B. Grzybowska, J. Haber, J. Komorek, J. Catal., volume 25, page 25 (1972)/A. P. V. Soares, L. K. Kimitrov, M. C. A. Oliveira, L. Hilaire, M. F. Portela, R. K. Grasselli, Appl. Catal. A, volume 253, page 191 (2003)/J. C. Jung, H. Kim, A. S. Choi, Y.-M. Chung, T. J. Kim, S. J. Lee, S.-H. Oh, I. K. Song, Catal. Commun., volume 8, page 625 (2007)]. However, a process of producing 1,3-butadiene using a pure bismuth molybdate catalyst by the oxidative dehydrogenation reaction of n-butene is difficult to be commercially used because it is limited to increase the yield of 1,3-butadiene using this process [Y. Moro-oka, W. Ueda, Adv. Catal, volume 40, page 233 (1994)]. Accordingly, in order to increase the activity of a bismuth molybdate catalyst to the oxidative dehydrogenation reaction of n-butene, research into a multi-component bismuth molybdate catalyst including various metal components in addition to bismuth and molybdenum has been made [M. W. J. Wolfs, Ph. A. Batist, J. Catal., volume 32, page 25 (1974)/S. Takenaka, A. Iwamoto, U.S. Pat. No. 3,764,632 (1973)].
Multi-component bismuth molybdate-based catalysts were reported in several documents and patents. Concretely, it was reported in the document [M. W. J. Wolfs, Ph. A. Batist, J. Catal., volume 32, page 25 (1974)] that 1,3-butadiene was obtained in a yield of 69% by performing an oxidative dehydrogenation reaction of n-butene using a composite oxide catalyst composed of nickel, cesium, bismuth and molybdenum at 520° C.; it was reported in the document [S. Takenaka, H. Shimizu, A. Iwamoto, Y. Kuroda, U.S. Pat. No. 3,998,867 (1976)] that 1,3-butadiene was obtained in a maximum yield of 62% by performing an oxidative dehydrogenation reaction of a C4 mixture including n-butane and n-butene using a composite oxide catalyst composed of cobalt, iron, bismuth, magnesium, potassium and molybdenum at 470° C.; and it was reported in the document [S. Takenaka, A. Iwamoto, U.S. Pat. No. 3,764,632 (1973)] that 1,3-butadiene was obtained in a maximum yield of 96% by performing an oxidative dehydrogenation reaction of n-butene using a composite oxide catalyst composed of nickel, cobalt, iron, bismuth, phosphorus, potassium and molybdenum at 320° C.
In a process of producing 1,3-butadiene using the multi-component bismuth molybdate catalysts reported in the above documents and patents, a high yield of 1,3-butadiene is obtained by using 1-butene, which is a n-butene isomer having relatively high reaction activity, as a reactant, or, when a C4 mixture including n-butane and n-butene is used as a reactant, a very complicated multi-component bismuth molybdate catalyst including six or more kinds of metal components combined in a predetermined ratio is used. That is, there is a problem in that metal components must be continuously added in order to increase catalytic activity, so that the structure of a catalyst is very complicated and the mechanism for preparing a catalyst is also complicated, with the result that it is difficult to repeatedly produce a catalyst.
Meanwhile, among the above composite oxide catalysts, other than the bismuth molybdate-based catalysts, the ferrite-based catalysts, which are known to have high activity in the oxidative dehydrogenation reaction of n-butane, have a spinel structure. Specifically, each of the ferrite-based catalysts is represented by AFe2O4 (A=Zn, Mg, Mn, Co, Cu or the like), and has a crystal structure in which oxygen (O) atoms constitute a cubic crystal, and A and Fe atoms are partially bonded between the oxygen (O) atoms [S. Bid, S. K. Pradhan, Mater. Chem. Phys., volume 82, page 27 (2003)]. This spinel-structured ferrite has an oxidation number of 2 or 3, and can be practically used as a catalyst for an oxidative dehydrogenation reaction for producing 1,3-butadiene from n-butene through the oxidation-reduction of iron ions and the interaction between oxygen ions in crystal and oxygen gases [M. A. Gibson, J. W. Hightower, J. Catal, volume 41, page 420 (1976)/R. J. Rennard, W. L. Kehl, J. Catal., volume 21, page 282 (1971)].
In relation to the oxidative dehydrogenation reaction of n-butene, the practical uses of ferrite-based catalysts were reported in several documents and patents. Concretely, it was reported in the document [R. J. Rennard, W. L. Kehl, J. Catal., volume 21, page 282 (1971)] that 1,3-butadiene was obtained in a yield of 41% by performing an oxidative dehydrogenation reaction of n-butene using a zinc ferrite catalyst, which is prepared by coprecipitation method and has a pure spinel structure, at 375° C.; it was reported in the document [J. A. Toledo, P. Bosch, M. A. Valenzuela, A. Montoya, N. Nava, J. Mol. Catal. A, volume 125, page 53 (1997)] that 1,3-butadiene was obtained in a yield of 21% by performing an oxidative dehydrogenation reaction of 5 mol % of 1-butene (5 mol % oxygen, 90 mol % helium) using a zinc ferrite catalyst at 420° C.; and it was reported in the document [B. L. Yang, D. S. Cheng, S. B. Lee, Appl. Catal. Volume 70, page 161 (1991)] that 1,3-butadiene was obtained in a yield of 47% by performing an oxidative dehydrogenation reaction of 1-butene (1-butene:oxygen:water:helium=2:4:20:38) using a magnesium ferrite catalyst at 450° C. Further, in methods of performing an oxidative dehydrogenation reaction using ferrite-based catalysts, the activity of n-butene in an oxidative dehydrogenation reaction was increased by additionally conducting pre-treatment and post-treatment in which additives are added to the catalyst or by physically mixing the catalyst with metal oxides to allow the catalyst to function as a co-catalyst [F.-Y. Qiu, L.-T. Weng, E. Sham, P. Ruiz, B. Delmon, Appl. Catal., volume 51, page 235 (1989)/L. J. Crose, L. Bajars, M. Gabliks, U.S. Pat. No. 3,743,683 (1973)/J. R. Baker. U.S. Pat. No. 3,951,869 (1976)/W.-Q. Xu, Y.-G. Yin, G.-Y. Li, S. Chen, Appl. Catal. A, volume 89, page 131 (1992)].
In addition to the methods of improving the activity of the ferrite-based catalysts by the methods of preparing the zinc ferrite catalyst through the pre-treatment, post-treatment and physical mixing as attempts to increase the activity of catalyst itself, methods of increasing the activity of a catalyst through the deformation of a spinel structure by partially replacing two-valence zinc cations or three-valence iron cations with other metal cations have been reported. In particular, it is reported in documents [J. A. Toledo, P. Bosch, M. A. Valenzuela, A. Montoya, N. Nava, J. Mol. Catal. A, volume 125, page 53 (1997)/R. J. Rennard Jr., R. A. Innes, H. E. Swift, J. Catal., volume 30, page 128 (1973)] that when a catalyst in which iron, as a three valence cationic component, is partially replaced with chromium or aluminum is used, catalytic activity is increased.
The above ferrite-based catalysts used in the oxidative dehydrogenation of n-butene are single-phase ferrite catalysts or multicomponent ferrite catalysts when other metal oxides acts as co-catalysts, and are prepared by coprecipitation. In methods of preparing a ferrite catalyst by coprecipitation, generally, the ferrite catalyst is synthesized by adding an aqueous solution of metal precursors and iron precursors, the aqueous solution including bivalent cations, to an excessive alkaline solution [L. J. Crose, L. Bajars, M. Gabliks, U.S. Pat. No. 3,743,683 (1973)/J. R. Baker, U.S. Pat. No. 3,951,869 (1976)].
In a process of producing 1,3-butadiene by performing an oxidative dehydrogenation reaction of n-butene using ferrite-based catalysts, pure single-phase ferrite catalysts have low activity compared to multi-component ferrite catalysts [J. A. Toledo, P. Bosch, M. A. Valenzuela, A. Montoya, N. Nava, J. Mol. Catal. A, volume 125, page 53 (1997)/R. J. Rennard Jr., R. A. Innes, H. E. Swift, J. Catal., volume 30, page 128 (1973)]. However, when ferrite catalysts partially substituted with metals or multi-component ferrite catalysts are used, 1,3-butadiene can be produced in a high yield compared to when pure single-phase ferrite catalysts are used. However, the ferrite catalysts partially substituted with metals or multi-component ferrite catalysts are difficult to be used commercially because they cannot be repeatedly prepared. Further, since a C4 mixture, which is a reactant used in the present disclosure, includes various components in addition to n-butane known to deteriorate the activity of a catalyst in the oxidative dehydrogenation reaction of n-butene [L. M. Welch, L. J. Croce, H. F. Christmann, Hydrocarbon Processing, page 131 (1978)], there is a problem in that side reactions may be conducted by various components constituting the multi-component ferrite catalyst.
Accordingly, the present Applicants developed a novel method of preparing a multi-component bismuth molybdate catalyst including only four kinds of metal components without undergoing complicated processes, the multi-component bismuth molybdate catalyst having excellent reproducibility and high activity in the oxidative dehydrogenation reaction of n-butene, and a novel method of preparing a single-phase zinc ferrite catalyst. To date, attempts to maximize the yield of 1,3-butadiene using the synergistic action attributable to the difference in reaction activity between the multi-component bismuth molybdate catalyst and the single-phase ferrite catalyst have never been reported.